Abstract: A tandem wheel suspension unit contained in a wheel well on a trailer. A frame is supported by a precompressed coil spring on the trunion shaft of a walking beam assembly, the walking beams having stops engaging said frame to normally prevent oscillation of the beams. The precompression of the supporting spring prevents one wheel from dropping into a highway chuckhole while permitting each wheel to rise in response to the impact shock upon striking an obstruction on the road.